1. Field of the Invention
The present invention relates to liquid crystal display devices and methods for driving the liquid crystal display devices. In particular, the present invention relates to field-sequential liquid crystal display devices and methods for driving the field-sequential liquid crystal display devices.
2. Description of the Related Art
As display methods of liquid crystal display devices, a color filter method and a field sequential method are known. In a color-filter liquid crystal display device, a plurality of subpixels which have color filters for transmitting only light of wavelengths with given colors (e.g., red (R), green (G), and blue (B)) are provided in each pixel. A desired color is expressed by control of transmission of white light in each subpixel and mixture of a plurality of colors in each pixel. In contrast, in a field-sequential liquid crystal display device, a plurality of light sources that emit lights of different colors (e.g., red (R), green (G), and blue (B)) are provided. A desired color is expressed by sequential lighting of the plurality of light sources and control of transmission of light of different colors in each pixel. In other words, the color filter method is a method by which a desired color is expressed by division of one pixel among lights of given colors, and the field sequential method is a method by which a desired color is expressed by division of a display period among lights of given colors.
The field-sequential liquid crystal display device has the following advantages over the color-filter liquid crystal display device. First, in the field-sequential liquid crystal display device, it is not necessary to provide subpixels in each pixel. Thus, the aperture ratio can be improved or the number of pixels can be increased. Further, in the field-sequential liquid crystal display device, it is not necessary to provide color filters. That is, light loss caused by light absorption in color filters does not occur. Therefore, transmittance can be improved and power consumption can be reduced.
Reference 1 discloses a field-sequential liquid crystal display device. Specifically, Reference 1 discloses a liquid crystal display device in which each pixel includes a transistor for controlling input of an image signal, a signal storage capacitor for holding the image signal, and a transistor for controlling transfer of an electrical charge from the signal storage capacitor to a display pixel capacitor. In the liquid crystal display device with the structure, writing of an image signal to the signal storage capacitor and display based on an electrical charge held in the display pixel capacitor can be performed concurrently.